Today's scientific literature is not limited to one single medium; various media have coexisted for some time. In recent years, an increasing number of publications have been published electronically. Electronic format alters the traditional way of publishing, retrieving, obtaining and preserving information, and it modifies the structure, composition and features of documents. Electronic publications are available in digital format and therefore require the use of a computer in order to access and use them. They can be delivered to users on physical media (diskette, CD-ROM, tape etc.), over networks (via electronic mail, ftp etc.) or may have to be accessed actively by users (typically on the World Wide Web). They can be made available in various formats with identical information and functionality in parallel. Various types of information (text, images, graphics, sound, software programs etc.) can be combined in one multimedia product. Embedded software may allow users to interactively modify underlying data or launch virtual experiments. Networked electronic publications can be accessed and used from anywhere at any time by several simultaneous users; interconnected documents provide links to other electronic resources. Depending on whether or not they can be modified after publication, electronic publications are dynamic or static documents.
In order to preserve the scientific and cultural knowledge of today, electronic publications have to be archived just as print publications have been. However, archiving electronic media is considerably different from archiving print publications. Up to now, archiving has been relatively easy and straight-forward. Libraries subscribe to journals and buy books, and after publications have arrived in our libraries, they are cataloged, classified, and technically prepared, and finally they are placed on the library shelves where they are available for users. References to print publications follow generally agreed-upon rules for citations that uniquely describe the source, and users can trust that a print document has not been changed after publication. Libraries own the publications they have bought, and unless it is decided to re-sell or remove the items, they are kept in the libraries indefinitely. Users can rely on a decentralized system of libraries where they can consult both current and historical publications whenever needed without additional costs.
In contrast, archiving electronic publications is much more complex. Up to now, no particular institution has been responsible for long-term preservation of electronic publications, hence future access to electronic documents is still uncertain. As of today, users don't know how they will be able to retrieve, obtain, and use electronic publications even a few years from now. Once archiving institutions have been selected, they must solve a large number of political, administrative and technological questions. What exactly has to be archived? Who provides and maintains the necessary tools and technological equipment? Who pays the personnel? Who will have access to the archives and at which costs? Is the technological infrastructure capable of meeting the demand for access to documents via networks?
Archives must guarantee that information resources can be identified, accessed, retrieved and used over time, and in the interest of the general public they must ensure access is available at reasonable costs. Archiving therefore is one of the most important and urgent problems arising from electronic publications and requires thoughtful solutions.